package cn.demoxy.filter;

import cn.demoxy.enums.ExceptionMessageEnum;
import cn.demoxy.exception.DemoException;
import cn.demoxy.model.entity.JWTToken;
import cn.demoxy.result.R;
import cn.demoxy.utils.JWTUtils;
import cn.demoxy.utils.RedisUtils;
import com.auth0.jwt.exceptions.TokenExpiredException;
import org.apache.shiro.authc.AuthenticationException;
import org.apache.shiro.authc.BearerToken;
import org.apache.shiro.authc.UnknownAccountException;
import org.apache.shiro.authc.UsernamePasswordToken;
import org.apache.shiro.web.filter.authc.BasicHttpAuthenticationFilter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import static cn.demoxy.enums.ExceptionMessageEnum.NO_LOGIN;
import static cn.demoxy.enums.ExceptionMessageEnum.NO_PERMISSION;

/**
 * @auther demo
 * @date 2022/6/13 21:35
 * 自定义JWTFilter
 */
public class JWTFilter extends BasicHttpAuthenticationFilter {

    /**
     * 判断用户是否想要登入。
     * 检测header里面是否包含Authorization字段即可
     */
    @Override
    protected boolean isLoginAttempt(ServletRequest request, ServletResponse response) {
        HttpServletRequest req = (HttpServletRequest) request;
        String authorization = req.getHeader("Authorization");
        return authorization != null;
    }

    /**
     *
     */
    @Override
    protected boolean executeLogin(ServletRequest request, ServletResponse response) throws Exception {
        HttpServletRequest httpServletRequest = (HttpServletRequest) request;
        String authorization = httpServletRequest.getHeader("Authorization");

        JWTToken token = new JWTToken(authorization);
        // 提交给realm进行登入，如果错误他会抛出异常并被捕获
        getSubject(request, response).login(token);
        // 如果没有抛出异常则代表登入成功，返回true
        return true;
    }

    /**
     * 这里我们详细说明下为什么最终返回的都是true，即允许访问
     * 例如我们提供一个地址 GET /article
     * 登入用户和游客看到的内容是不同的
     * 如果在这里返回了false，请求会被直接拦截，用户看不到任何东西
     * 所以我们在这里返回true，Controller中可以通过 subject.isAuthenticated() 来判断用户是否登入
     * 如果有些资源只有登入用户才能访问，我们只需要在方法上面加上 @RequiresAuthentication 注解即可
     * 但是这样做有一个缺点，就是不能够对GET,POST等请求进行分别过滤鉴权(因为我们重写了官方的方法)，但实际上对应用影响不大
     */
    @Override
    protected boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue) {
        if (isLoginAttempt(request, response)) {
            try {
                executeLogin(request, response);
            } catch (Exception e) {
                String msg = e.getMessage();
                Throwable cause = e.getCause();
                if (cause != null && cause instanceof TokenExpiredException) {
                    //AccessToken过期，尝试去刷新token
                    String result = refreshToken(request, response);
                    if (result.equals("success")) {
                        return true;
                    }
                } else {
                    response403(request, response);

                }
            }
        }
        return true;
    }

    /**
     * 对跨域提供支持
     */
    @Override
    protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception {
        HttpServletRequest httpServletRequest = (HttpServletRequest) request;
        HttpServletResponse httpServletResponse = (HttpServletResponse) response;
        httpServletResponse.setHeader("Access-control-Allow-Origin", httpServletRequest.getHeader("Origin"));
        httpServletResponse.setHeader("Access-Control-Allow-Methods", "GET,POST,OPTIONS,PUT,DELETE");
        httpServletResponse.setHeader("Access-Control-Allow-Headers", httpServletRequest.getHeader("Access-Control-Request-Headers"));
        // 跨域时会首先发送一个option请求，这里我们给option请求直接返回正常状态
        if (httpServletRequest.getMethod().equals(RequestMethod.OPTIONS.name())) {
            httpServletResponse.setStatus(HttpStatus.OK.value());
            return false;
        }
        return super.preHandle(request, response);
    }

    /**
     * 将非法请求跳转到 /403
     */
    private R response403(ServletRequest req, ServletResponse resp) {
        HttpServletResponse httpServletResponse = (HttpServletResponse) resp;
        return R.build(403, "权限不足,禁止操作!");

    }

    /**
     * 这里的getBean是因为使用@Autowired无法把RedisUtil注入进来
     * 这样自动去注入当使用的时候是未NULL，是注入不进去了。通俗的来讲是因为拦截器在spring扫描bean之前加载所以注入不进去。
     * <p>
     * 解决的方法：
     * 可以通过已经初始化之后applicationContext容器中去获取需要的bean.
     */
    public <T> T getBean(Class<T> clazz, HttpServletRequest request) {
        WebApplicationContext applicationContext = WebApplicationContextUtils.getRequiredWebApplicationContext(request.getServletContext());
        return applicationContext.getBean(clazz);
    }

    /**
     * 刷新token
     */
    private String refreshToken(ServletRequest request, ServletResponse response) {
        HttpServletRequest req = (HttpServletRequest) request;
        RedisUtils redisUtils = getBean(RedisUtils.class, req);
        //获取传递过来的accessToken
        String accessToken = req.getHeader("Authorization");
        //获取token里面的用户名
        String username = JWTUtils.getUsername(accessToken);
        System.out.println("username" + username);
        //判断refreshToken是否过期了，过期了那么所含的username的键不存在
        long size = redisUtils.lGetListSize("user");
        for (long i = 0; i < size; i++) {
            Map<String, Object> onlineUser = (Map<String, Object>) redisUtils.lGetIndex("user", i);
            if (onlineUser.get("username").equals(username)) {
                //获取当前时间节点
                redisUtils.lRemove("user",1,onlineUser);
            }
        }
        long currentTimeMillis = System.currentTimeMillis();
        //生成刷新的token
        String token = JWTUtils.sign(username, currentTimeMillis);
        //刷新redis里面的refreshToken,过期时间是30min
        Map<String, Object> item = new HashMap<>();
        item.put("username", username);
        item.put("ms", currentTimeMillis);
        redisUtils.lSet("user", item, 60 * 30);
        //再次交给shiro进行认证
        JWTToken jwtToken = new JWTToken(token);
        try {
            getSubject(request, response).login(jwtToken);
            // 最后将刷新的AccessToken存放在Response的Header中的Authorization字段返回
            HttpServletResponse httpServletResponse = (HttpServletResponse) response;
            httpServletResponse.setHeader("Authorization", token);
            httpServletResponse.setHeader("Access-Control-Expose-Headers", "Authorization");
            return "success";
        } catch (Exception e) {
            return e.getMessage();
        }
    }

}